Flight Theory and Aerodynamics. Joseph R. Badick

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654.9 0.000 169 4 000 0.8881 0.9424 0.8637 44.74 0.9725 652.6 0.000 174 5 000 0.8617 0.9283 0.8320 41.17 0.9656 650.3 0.000 178 6 000 0.8359 0.9143 0.8014 37.60 0.9587 647.9 0.000 182 7 000 0.8106 0.9004 0.7716 34.04 0.9519 645.6 0.000 187 8 000 0.7860 0.8866 0.7428 30.47 0.9450 643.3 0.000 192 9 000 0.7620 0.8729 0.7148 26.90 0.9381 640.9 0.000 197 10 000 0.7385 0.8593 0.6877 23.34 0.9312 638.6 0.000 202 15 000 0.6292 0.7932 0.5643 5.51 0.8969 626.7 0.000 229 20 000 0.5328 0.7299 0.4595 −12.32 0.8625 614.6 0.000 262 25 000 0.4481 0.6694 0.3711 −30.15 0.8281 602.2 0.000 302 30 000 0.3741 0.6117 0.2970 −47.98 0.7937 589.5 0.000 349 35 000 0.3099 0.5567 0.2353 −65.82 0.7594 576.6 0.000 405 36 089^a 0.2971 0.5450 0.2234 −69.70 0.7519 573.8 0.000 419 40 000 0.2462 0.4962 0.1851 −69.70 0.7519 573.8 0.000 506 45 000 0.1936 0.4400 0.1455 −69.70 0.7519 573.8 0.000 643 50 000 0.1522 0.3002 0.1145 −69.70 0.7519 573.8 0.000 818

      ^a The tropopause.

ALTITUDE MEASUREMENT

      When a pilot uses the term altitude, the reference is usually to altitude above sea level as read on the altimeter, but it is important that the distinction is made to understand what types of altitude exist. When meteorologists refer to the height of the cloud layer above an airfield, they are usually referring to the altitude above the field elevation. When air traffic control refers to an altitude at FL180 and above, they are referring to pressure altitude. A flight crew in an aircraft approaching the runway during a low ceiling CAT III instrument approach will need to understand the value of a radar altimeter. Understanding what “altitudes” are important at different periods of flight, and the effect of temperature, pressure, and moisture on those altitudes, is imperative for safe flight.

      Indicated Altitude

      Indicated altitude is the altitude that is read directly from the altimeter and is uncorrected for any errors. In the United States, below FL180 the altimeter is set to the current altimeter setting of the field you are departing from or arriving to, or is given by air traffic control for the current area you are flying in. In the United States, when flying at or above 18 000 ft, altitude is measured in Flight Levels (e.g. FL180 for 18 000 ft). At FL180, the indicated altitude will be equal to pressure altitude as the altimeter setting is set to 29.92″, standard pressure, or QNE. The altitude at which the crew changes to 29.92 is called the transition altitude (TA). When the crew descends for landing, the altitude at which they return the altimeter setting to local barometric pressure corrected to sea level (QNH) is called the transition level (TL). (Remember it this way: 29.92 is selected at the TA, and the “A” stands for aloft, as in climbing or cruise. When returning to land, the TL is set on descent, and “L” stands for low, or landing.)

      When QNE is lower than 29.92, the lowest usable flight level is no longer FL180. The lowest usable FL is obtained from the aeronautical publications. For instance, in the United States, if the pressure in the area of operations is between 29.91 and 29.42″, the lowest usable enroute altitude is FL185. It should also be noted that the TA and TL outside the United States will not

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